It is generally desirable to observe, watch and predict the physiological state of an animal, in particular a farm animal. Thus, body fluids of animals, in particular milk, urine and blood may be analysed in order to obtain values of parameters, such as cell count in milk, lactate dehydrogenase (LDH), N-Acetyl-β-D-glucosaminidase (NAGase), ketone bodies such as acetoacetate, beta-hydroxybutyrate (BHB) and acetone, urea content, progesterone, or others, each of which by itself or in combination with others indicates a certain physiological state. For example, a high LDH concentration usually indicates mastitis, whereas the progesterone content may indicate a pregnancy state.
The prior art has proposed various methods for analysis of milk samples. For example, U.S. Pat. No. 5,252,829 discloses a method for determining the amount of urea in milk. In a milk sample, the absorption of infrared radiation in various wavelength intervals are determined, whereby urea, fat, lactose, and protein absorb in different wavelength intervals.
U.S. Pat. No. 6,405,672 and de Mol (2000) discloses a system and a method for monitoring the physical condition of a herd of livestock, errors between values predicted in accordance with a time-series model and corresponding measured values are used for determining a confidence interval for a prediction for each animal individually the significance of an error between a prediction and a measured value regarding the likelihood that the animal is in heat or suffers from a disease is automatically assessed for each animal individually.